﻿There should be only a maximum of one material association assigned to an building element.
<blockquote class="note">NOTE&nbsp; The material association can assign a single material, a set of materials, a set of material layers, or a set of material profiles by a single association relationship.</blockquote>
<blockquote class="change-ifc2x4">FC2x4 CHANGE The where rule has been promoted from the subtype <em>IfcWall</em>.</blockquote>
